Undermined driveways. Misplaced gutters or missing downspouts often dump water alongside a driveway or sidewalk. Over time, the flowing water may erode the ground next to the driveway, and then underneath it. As the earth beneath the driveway washes away, the driveway loses its support and is likely to crack and settle. Before replacing such a driveway, first fix the water flow problem. See the gutter installers and waterproofing contractors sections for more information.
Contraction joints. As concrete sets and hardens, it has a tendency to shrink, and therefore crack. Contraction joints are shallow grooves cut into a concrete slab soon after it is placed. This way, when the concrete hardens and shrinks, any cracking that arises should tend to follow the contraction joints, where the concrete is thinner and weaker. In temperate climates, experts recommend cutting contraction joints approximately every 15 feet.
Expansion joints. Expansion joints are placed at intervals of about 75 feet, on very large slabs of concrete. These joints extend through the entire thickness and width of the slab, and are filled with fiberboard and sealed. Expansion joints help prevent concrete cracking by giving room for thermal expansion in hot weather. Like a contraction joint, an expansion joint can prevent cracks from propagating across the joint. However, even with proper joints, driveways often crack. Due to the variability of materials and terrain, many established companies will not guarantee their driveways against aesthetic cracking.
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